Heliox and oxygen reduce infarct volume in a rat model of focal ischemia

Normobaric hyperoxia treatment has recently been demonstrated to be remarkably beneficial in acute focal ischemia. The present study compared hyperoxia treatment with a novel heliox treatment. Adult male rats breathed 30% oxygen and 70% nitrogen (control group), 100% oxygen (hyperoxia group), or 30% oxygen and 70% helium (heliox group) during a middle cerebral artery occlusion for 2 h and a 1-hour reperfusion (n = 6 in each group). Neurological deficits were scored at 3 and 24 h post focal ischemia. Neither the physiological parameters (body temperature, blood pressure, heart rate, O2 saturation, and laser Doppler cerebral blood) nor the 3-hour post ischemia neurological scores differed between groups. However, the neurological scores showed a statistically significant improvement at 24 h post ischemia in the heliox group (p < 0.05). The infarct volume (mean + SD) as measured by 2,3,5-triphenyltetrazolium staining included 36 ± 17% of the involved hemisphere in the control group, 16 ± 14% in the hyperoxia group, and 4 ± 2% in the heliox group (p < 0.01). In conclusion, whereas hyperoxia reduced the infarct volume, heliox further reduced the infarct volume and improved 24-hour neurological deficits in a rat model of focal ischemia. This suggests that a greater benefit may accrue from heliox therapy.